<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
//     let a="haha"
//     let b='xixi'
//     // alert(a+b)
//      let c="haha'hha'"
//    //let c='haha"hhh"'
//     // alert(c.length)
//    // alert(a+10)
//     //alert(100+100)
//     alert('100'+100)
console.log(typeof("hello"+1))
console.log(typeof("hello"+true))
let b
console.log(typeof("hello"+b))
let c=null
console.log(typeof("hello"+c))


</script>
</html>